Electrical condenses and method of making the same



June 24, 1930 R Q SPRAGUE 1,768,333

ELECTRICAL CONDENSER AND METHOD OF MAKING THE SAME Filed Dec. 13, 1927 Patented June 24. 1930 UNITED STATES PATENT OFFICE ROBERT C. SPBAGUE, ,OI QUINCY, MASMCHUSETTS, .ASSIGNOB TO SPRAGUE SPECIAL,- mms (fl OI QUINCY, MASSACHUSETTS, A CORPORATION 01' IASSACHUSETTS ILEQIRICAL CONDENSER AND METHOD OF MARIN G THE SAME Application filed December 13, 1927. Serial'llo. 839,884.

This'invention is particularly ap licable to condensers such as that disclosed in my companion application Serial No. 135,342, filed September 14, 1926, of -which this application is in part a continuation, but it is to be understood that the present invention is applicable to other condensers as well.

Objects of the invention are to provide a condenser which is simple and economical to construct but which is efficient and durable in use, which does not require a metal container or other housing such as ordinarily employed, which has an effective and permanent electrical contact between the terminals and conductive layers, which has durablev terminals permanently anchored in the body of the condenser so as not to break off or pull out, which is free from the likelihood of short circuit, and generally to improve the art of condensers.

Prior to the invention of the aforesaid application it was customary to house condensers of the wound foil type in a tin canv or other rigid container an to mount the 5 condenser terminals on the container, the wound condenser inside the container merely being provided with light terminal strips for connecting the foil stri s with the terminals on the container.

not onl greatly increased the cost of material an labor in the process of manufacture, but it has added largely to the bulk and weight of the resultin product. Moreover, the aforesaid termina strips connectin the foil strips with the container terminals ave been very thin, being little if 'an heavier than the foil windings, so" that t ey often tear off or pull out in assembling or repairingta condenser, the stripsnecessarily bein and thin to avoid cutting the foil woun therearound. p I

'According to my invention, the container and second set of terminals carried thereby are eliminated by mounting heavy terminal strips directly in the body of the condenser his practice has ment illustrated in the accompanying drawin such a way that they do not tend to puncture the insulating strips between the foil strips, donot pull out, and therefore serve as the ultimate terminals of the condenser, even to the extent of su orting the condenser as is often desira lile in radio sets. This is accomplished by pressing the relatively heavy terminal strips into recesses in a core of fiber-board or the like, or by striking up projections on the terminahstrips which either pinch the core or wedge into recesses previously formed in the core. The inner ends of the foil strips are preferably inserted under the terminals respectively before the latter are pressed into the core, thereby anchoring the ends of the foil strips (and their intermediate insulating strips to the core) which greatlyfacilitates the process of winding the strips on the core.

Another unique characteristic of this invention consists in arranging the terminal strips obliquel in approximately parallel offset relations ips so that they may extend a greater distance into the condenser, on the same side of the core, if desired, and at the same time project from the ends of the condenser approximately midway between the sides or lateral edges, thereby protecting the projecting portions from accidental breakage and facilitating the mounting of the condenser by means of the terminals. Other objects and advantages of the present invention will be evident from the followin description and preferred embodiin s, in which f ig. 1 is a plan view of the condenser core;- f

Fig. 2 is a section on line 22 of Fig. 1; Fig. 3 is a plan view of terminal member; Fig. 4 is a section on line of Fig. 3;, Fig. 5 isa plan view of a partially completed-condenser, showing. one terminal and one set of foil'and insulating strips applied tothecore;

Fig. 6 is a similar view showin the end of the first set folded over and t e second set of foil and insulating strips, together with the second terminal, applied;

Fig. 7 is a view similar to Fig. 6 showing the second set of foil and insulating strips folded over preparatory to winding. both sets around the core in the same direction;

Fig. 8 is a section on line 8-8 of Fig. 7

Fig. 9 is a central transverse section of the completed condenser; and

Fig. 10 is a central longitudinal section of a slightly modified condenser havin a greater number of turns and having di 'erently shaped terminals.

The particular embodiment of the invention chosen for the purpose of illustration comprises a core C formed of fiber board or other suitable material and having in one face thereof two oblique grooves 1 and 2 meeting the ends of the core approximately midway between the lateral ed es. In addition to the recesses 1 and 2 t e core also has recesses 3 and 4, preferably extending all the way through the core, to receive prongs or other projections on the terminals.

The terminals may be shaped in various ways depending upon the way the condenser is to be mounted or connected in circuits but in general they are. preferably characterized by a thickness depending upon the rigidity required, the depth of the grooves 1 and 2 being made to correspond, by prongs tightly fitting in the recesses 3 and 4:, and

r by end projections which are oblique to the portions fitting in the grooves so as to project at right angles to the ends of the core. A typical terminal is shown in Figs. 3 and 4 comprising a body portion 5 adapted to fit in one of the grooves of the core, struck up prongs 6 adapted to fit in the recess 3 or 4 and an oblique end projection having an opening 7 for connection to a circuit and an opening 8 for mounting the terminal. The terminal is preferably formed of relatively stiff metal, such as copper of sufiicient thickness to render the terminal fairly stiff, and the prongs 6 are preferably tapered so as to wedge tightly in the openings 3 or 4.

The conducting and insulating strips are referably in the form of very thin metal oil tissue paper lightly cemented together with paraffin or other suitable adhesive, as disclosed in my aforesaid application, so that these strips may be readily wound as a single composite strip, each comprising a foil strip and one or more paper stri s. It will of course be understood that the oil of one set will contact with one terminal and the foil of the second set with the other terminal. In Figs. 5 to 10 the foils of the two strips are designated F and F and the pa er component as P and P.

shown in Fig. 5, one set of foil and paper strips is first applied to the core and one terminal is then applied over the set of strips with the paper next to the core and the foil contacting with the terminal. Upon pressing the terminal into the groove the prongs 6 puncture the strip and embed themselves in the recesses 3 tightly enough to hold the parts together during the succeeding operations in winding the con denser. The inner end of the strip, which is preferably cut obliquely as shown in Fig. 5, is then folded over the terminal T, thereby to establish good electrical contact be tween the foil and both sides of the terminal as well as to protect the succeeding turns of the winding by virtue of the folded-over ends between the terminal and the succeeding windings. After the first strip and terminal have been applied as described, the second terminal and strip are similarly a plied as illustrated in Figs. 6, 7 and 8. T e two composite strips PF and PF are then wound around the core clockwise (Fig. 8) until the composite strips have been completely wound around the core. The outer end of the inner strip P-F is then folded outwardly under the outer end of the outer strip P'-F as shown in Fig. 9 so that the foil F of the outer strip can not contact with the foil F of the inner strip at the end of the outer strip as it otherwise might do if the foil F of the outer strip were slightly longer than the taper P of the outer strip. v

After the composite strips have been completely wound as aforesaid" an insulating wrapper V is applied over the com osite. strips. This wrapper is a relatively eavy sheet of paper thoroughly waterproofed as with asphalt, as described in my aforesaid application. The condenser is then preferably dipped in high temperature parafiin to drive out all the air and to thoroughly impregnate the condenser, whereupon it is transferred to a cooler bath of paraffin to reduce the temperature of the impregnation material to the point where it will not run out when the condenser is finally removed. The condenser is then preferably compressed to drive out excess impregnatlon material and reduce it to a standard thickness and,

after the exterior of the condenser and the projecting portions of the terminals have been cleaned, the condenser is ready for use.

In the modification shown in Fig. 10 the terminals are'made somewhat longer and are so shaped that the condenser may be mounted on a flat surfaoe'by means of the terminals as is ofttimes desirable in radio practice. Fig. 10 also illustrates the fact that the wrapper W is somewhat longer than the width of the composite strips, preferably being substantially equal to the length of the core, so that the space at each end of the wound strips may be filled with of alternate layers of insulating and conducting .material, and two terminals extending obliquely to the lateral ed es of the body in approximately parallel 0 set relationship and projecting respectively from the opposite end edges of the body approxi mately midway between the lateral edges.

2. condenser comprising two terminals with insulated layers of foil wrapped therearound, the terminals extending obliquely in approximately parallel offset relationship within the body of foil and projecting approximately centrally from opposite ends of said body.

3. A condenser comprising a core having terminal recesses extending obliquely to the ateral edges in ofi'set relatlonship and meeti g the end edges approximately midway between the lateral edges, terminals disposed in said recesses and projecting from layers of foil wrapped laterally around said core with their inner ends respectively exteriisiing into said recesses under said termina 4. A condenser comprising a core having terminal recesses extending obliquely to the lateral edges in offset relatlonship and meeting the end edges approximatel midway between the lateral edges, termina disposed in said recesses and projectin from the end ed es of the core, and insu ated layers of foil wrapped laterally around said core with their inner ends respectively extending into said recesses under said terminals and thence. folding over the terminals.

5. A condenser comprising a core having terminal recesses in its periphery, terminals disposed in said recesses, and insulated layers of foil wrapped around said core with their inner ends respectively extending into. said recesses under said terminals and thence folding back over the terminals and thence over said periphery.

6. A condenser comprising a core having setsof superposed insulating and foil strips wound therearound, the inner ends of one set being folded foil to foil under the inner ends of the other set and the outer ends of one set being similarly folded'under the outer ends of the other set.

7. A condenser comprising a core having sets of superposed insulating and foil strips wound therearound, the inner ends of each set being folded foil to foil and the outer ends of one set being similarly folded under the outer ends of the other set.

8. A condenser comprising a core having two sets of superposed insulating and foil strips wound therearound' in the samedirection with the foil strip outermost in each set, and the outer end of the inner set being folded outwardly foil to foil under the outer end of the outer set.

Signed by me at Quincy, Massachusetts, this 8th day of December, 1927.

ROBERT C. SPRAGUE.

the end ed es of the core, and insulated 

